钛硅分子筛催化气相环己酮肟贝克曼重排反应

Gas-Phase Beckmann Rearrangement of Cyclohexanone Oxime Catalyzed by Titanium Silicalite

对比研究了具有MFI结构的TS 1,silicalite 1,Al ZSM 5和B ZSM 5分子筛对气相环己酮肟贝克曼重排反应的催化性能 .结果显示 ,TS 1适宜用作重排反应的催化剂 ,而含骨架B或Al的ZSM 5分子筛的催化性能较差 ,表明将Ti引入至sili calite 1有利于改善其对环己酮肟重排反应的催化性能 .反应氛围 (溶剂、载气和原料添加物 )对TS 1催化性能的影响规律说明 ,弱酸性气体的存在有利于TS 1对环己酮肟的活化与己内酰胺的选择性生成 .优化的反应氛围包括以甲醇或乙醇为溶剂 ,二氧化碳为载气 ,以及醋酸为原料添加物 .

Four different molecular sieves with MFI structure, TS-1, silicalite-1, Al-ZSM-5 and B-ZSM-5, were tested for the gas-phase Beckmann rearrangement of cyclohexanone oxime (CHO) into caprolactam. TS-1 shows higher CHO conversion, lactam selectivity and stability than the other three samples. Silicalite-1 exhibits better catalytic performance for the rearrangement reaction than Al-ZSM-5 and B-ZSM-5. These results suggest that it is the incorporation of Ti into the framework of silicalite-1 that improves its catalytic efficiency for the rearrangement reaction, while the insertion of Al or B shows a negative effect on the Beckmann reaction. The effects of solvent, additive and carrier gas on the performance of TS-1 were also investigated. The presence of acidic acetic acid or carbon dioxide in the reaction system increases the CHO conversion and lactam selectivity. But the addition of basic aniline or ammonia in the system reduces the CHO conversion and lactam selectivity. This indicated that the weakly acidic chemical environment is beneficial to the rearrangement. The optimal reaction conditions include using methanol or ethanol as the solvent, carbon dioxide as the carrier gas and acetic acid as the additive.